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Date: Wed, 10 Mar 2021 10:04:29 -0600
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Subject: Re: [PHP-DEV] [VOTE] Fibers
From: aaron@trowski.com (Aaron Piotrowski)


> On Mar 10, 2021, at 4:56 AM, Peter Stalman <sarkedev@gmail.com> wrote:
>=20
> On Tue, Mar 9, 2021 at 6:03 PM twosee <twose@qq.com> wrote:
>=20
> 5. Not compatible with Swoole
>=20
> In my opinion, Swoole is an important part of the PHP ecosystem. But =
now, Fiber cannot work with Swoole. And based on the above reasons, =
Swoole will not consider compatible fiber.
>=20
> We would expect some ZendAPI rather than Fiber extensions to provide =
support for coroutine switching.
>=20
>=20
>  Hi Twosee,
>=20
> Are you saying that by adding this Fiber code to core it will prevent =
Swoole from functioning? If so, that is concerning.  Or are you simply =
saying that Swoole doesn't like this implementation and will not use it =
with their own code?
>=20
> One thing to consider when comparing the Fiber implementation is that =
the vast majority of PHP applications are still run behind a web server =
in short-lived requests.  Unlike Swoole, Swow, and Parallel, it isn't =
limited to ZTS or CLI.  It might not be the ideal solution, but IMO it =
is a step in the right direction for PHP to allow for better async =
support.
>=20
> And I think you are right that "Fiber is just an enhancement of =
Generator'', but so what?  The Generator addition in 5.5 opened up PHP =
to a hacky way of doing async, but it worked everywhere.  Fiber allows =
that to be much more convenient in switching contexts deep inside a call =
stack.  I don't think it needs to be the end-all-be-all coroutine =
solution to rival Goroutines, and I'm pretty sure it's not trying to be.
>=20
> Thanks,
> Peter
>=20

Hello,

This Fiber implementation does not conflict with Swoole. Both could =
coexist. However, Swoole's implementation does provide some other =
features that this does not, so I believe Twosee was simply saying that =
Swoole cannot directly use this fiber implementation. My focus was to =
provide a minimalistic implementation in core so user space code can =
make other API decisions as they saw fit.

Regarding some of the other concerns raised:

- Switch notification: The observer notification is triggered before =
switching to a fiber and after suspending from a fiber. The timing here =
was an open question I've discussed with others and we planned to =
examine it later. Moving the second notification before suspending the =
second fiber was already being considered. As this was an internal API I =
felt it was not needed directly in the RFC.
- Fiber is final, as is Generator. I believe it is better to compose =
classes rather than extend them. Of course it is always possible to =
remove final.
- Using Fiber::resume() and Fiber::suspend() models fibers as a stack =
and simplifies logic of resuming/suspending fibers. Ruby fibers share =
this exact API, though their API uses the term yield instead of suspend.
- State functions: Separate methods (i.e., isRunning, isTerminated) =
returning a boolean are preferable IMO to comparing integer constants to =
a value returned by a status method. This is really a matter of opinion =
than one being strictly better than the other.
- Pure C coroutine: The extension code provides user space fibers. =
Adding functions to create fiber C-only fibers can certainly be done if =
the need arises.
- Being marked experimental: I was hoping this would be a good =
compromise between allowing people to experiment with fibers and =
providing the ability to make minor BC breaks if the need arose. I =
realize this is generally not the PHP way, however this is, IMO, not =
entirely without precedent. JIT and FFI were not widely used before =
being added to PHP.

Thanks for the feedback!

Aaron Piotrowski